This application relates generally to gas turbine engines and, more particularly, to methods and apparatus for operating gas turbine engines.
Gas turbine engines typically include a high pressure rotor assembly including at least two rotor stages. Each rotor stage includes a plurality of circumferentially spaced rotor blades in flow communication with a combustion gas flowpath extending through the rotor assembly. A plurality of cavities defined within the rotor stages are radially inward from the rotor blades and the combustion gas flowpath. More specifically, these cavities are forward and aft of each rotor stage.
Power output of gas turbine engines is limited by a corrected speed of the turbine engine. More specifically, the turbine engine corrected speed limit is based on a necessity to maintain a positive pressure margin, known sometimes as a purge margin, through the rotor assembly cavities. If purge margin is not maintained through the cavities, ingestion may occur within the rotor assembly, causing an operating temperature within the cavities to increase. Over time, operating with high cavity temperatures may result in premature failure of turbo-machinery hardware.
To minimize the potential risks associated with ingestion, engine purge margins are typically pre-set by empirical methods based on historical trends. As a result of the pre-set purge margins, a maximum operating level of the gas turbine engine is limited. Furthermore, an operating capacity of the gas turbine engine is also limited.
In an exemplary embodiment, a gas turbine engine includes a temperature sensor assembly that continuously monitors an operating temperature within cavities defined within a multi-stage rotor assembly of the turbine engine. The temperature sensor assembly includes a plurality of temperature sensor assemblies that monitor the temperature within each rotor assembly cavity. Each temperature sensor assembly includes a plurality of support guide tubes attached to the engine to extend from an outer casing of the engine to each cavity. A temperature sensor is inserted through the support guide tubes and positioned within each cavity.
During engine operation, each rotor assembly cavity receives cooling bleed air from the engine. The temperature sensor system continuously monitors the operating temperature within the cavities. A maximum power setting for the engine is determined based on the purge margin through the cavities. More specifically, the maximum power setting is determined by continuously monitoring the operating temperature within the cavities, and increasing the operating level of the engine in response to the temperature within the cavities to a point where ingestion is imminent. As a result, the gas turbine engine may be operated at a maximum power level that is determined based on the operating characteristics of the engine and not pre-set using historical data.